1. Field of the Invention
This invention is related to application Ser. No. 264,413, filed Oct. 31, 1988. This invention relates to the production of aminoacetonitriles, and more specifically to an integrated process wherein a crude, unpurified hydrogen cyanide product gas stream from a hydrogen cyanide process reactor together with a formaldehyde stream, optionally, a crude, unpurified formaldehyde product gas stream from a formaldehyde process reactor, are fed directly into a reactive absorber, together with an additional nitrogen source and scrubbed with a controlled-pH, aqueous solution to produce aminoacetonitriles in high yields. This process provides improved economics for the production of aminoacetonitriles by eliminating the costly recovery and purification processes associated with conventional hydrogen cyanide and formaldehyde production processes.
2. Background
It is known in the prior art that aminoacetonitriles can be prepared by reacting formaldehyde and hydrogen cyanide together with a nitrogen source in liquid phase. For example, nitriloacetonitrile can be produced by this method as shown in the following general reaction: ##STR1##
Similarly, EP 0 102 343 Al teaches a process for producing nitrilotriacetonitrile from an ammonia derivative, formaldehyde and hydrogen cyanide. In this process hydrogen cyanide is scrubbed from a gas stream with an aqueous solution containing nitrilotriacetonitrile mother liquor to produce a hydrogen cyanide containing solution. To this hydrogen cyanide containing solution is added formaldehyde and an ammonia derivative selected from the group consisting of ammonia, an ammonium salt, and hexamethylenetetraamine to produce a reaction mixture. This reaction mixture is then reacted to produce nitrilotriacetonitrile in approximately 88-97.5% yields.
EP 0,102,935 teaches a process for producing nitrilotriacetonitrile from an ammonia derivative, formaldehyde and hydrogen cyanide. In this process the hydrogen cyanide is scrubbed from a gas stream containing hydrogen cyanide with a dilute solution of a mineral acid to produce a hydrogen cyanide containing solution. To this hydrogen cyanide containing solution is added an ammonia derivative selected from the group consisting of ammonia, an ammonium derivative, and hexamethylenetetramine to produce a reaction mixture. This reaction mixture is then reacted to produce nitrilotriacetonitrile.
On an industrial scale, the conventional processes for the production of aminoacetonitriles require purified, commercial grade liquid hydrogen cyanide and formaldehyde in high concentration in order to obtain product in high enough yield to warrant economic feasibility. Substantial engineering considerations and capital equipment costs can be attributed to the recovery and purification equipment required to obtain commercially pure formaldehyde and hydrogen cyanide. For example, in the production of hydrogen cyanide, the crude product gas stream contains, in addition to hydrogen cyanide, a significant amount of ammonia. In conventional manufacturing methods the ammonia must always be removed to avoid the dangerous exothermic polymerization of the liquid hydrogen cyanide.
Similarly, in the production of formaldehyde, the crude reactor product stream is a dilute gaseous mixture of formaldehyde and water which requires large absorption columns to recover formaldehyde in sufficient purity.
It has now been discovered that aminoacetonitriles can be produced using crude, unpurified gaseous product streams from formaldehyde and hydrogen cyanide reactors directly without the need of purifying these reactive product streams. Under the process of this invention, it is no longer necessary, and is actually redundant to remove the unreacted ammonia gas from the hydrogen cyanide product gas stream as a purification step, only to add it later in the downstream production of aminoacetonitriles. This also applies to the excess water in each of the hydrogen cyanide and formaldehyde processes. That is, since the reactants in the aminoacetonitrile production process must be diluted in water prior to their reactions, it is redundant to remove water from the crude unpurified reactor product streams.